Active Settlement Control with Compensation Grouting—Results from a Case Study

Near surface tunnelling in built-up urban areas has lead to the development of special geotechnical measures to protect buildings from damage resulting from undue (total and differential) settlements. In contrast to passive ground improvement techniques, compensation grouting is an active method applied to counteract subsidence induced by tunnel excavation. Compensation grouting is done in two stages: In the first stage grouting between the ground surface and the tunnel is performed for "conditioning" the soil. After the immediate response of the system is ensured, settlements monitored with accurate measurement devices are compensated in the actual grouting phase. In this paper compensation grouting operations for a tunnel excavation underneath a station building are described in a case study. The efficiency of compensation grouting is discussed for this practical example. To show the basic effects of compensation grouting, finite element calculations are provided for different stages of the grouting process and compared with in-situ measurements.